Electronic and crystalline structures of zero band-gap LuPdBi thin films grown epitaxially on MgO(100)

Thin films of the proposed topological insulator LuPdBi—a Heusler compound with the C1b structure—were prepared on Ta-Mo-buffered MgO(100) substrates by co-sputtering from PdBi2 and Lu targets. Epitaxial growth of LuPdBi films was confirmed by X-ray diffraction and reflection high-energy electron diffraction. The root-mean-square roughness of the films was as low as 1.45 nm, even though the films were deposited at high temperature. The film composition is close to the ideal stoichiometric ratio. The valence band spectra of the LuPdBi films, observed by hard X-ray photoelectron spectroscopy, correspond very well with the ab initio-calculated density of states.